Best cartridge

Given the turntable and phono preamp a MM Ortofon would be fine

Ahhh...another seeker of the Holy Grail!  Sorry for the sarcasm, but based on your investment in digital music I am going to gently advise caution.  This is coming from someone who has a vinyl preference.  Take stock of your goals first because to reach sound parity or even approach it will require quite a bit of time and money.  A good first order approximation might be a ratio of 10:1.  That is it will cost about 10x as much to reach sound parity for a good analog front end as it does for your digital one and to get there is not all about $ because unlike digital, which is plug and play, analog requires a lot of effort based on expertise which does not grow on trees.  So, before you embark on this adventure be sure of what you want and why you want it.  If you already owned a lot of vinyl it would be one thing, but you don't.  If there is music that you wish to acquire that is only available on vinyl, then your quest makes perfect sense.  If you have convinced yourself that the sound of vinyl is sublime to the point that nothing else will do, you are lost to logic.  Welcome to the club.  My point is, first and foremost know thyself.
Understanding that advice is more than you wanted to know, the simple answer to your question is to go to Amazon or LP Gear and buy an Audio Technica moving magnet cartridge that costs somewhere around $100 to $200 (at the most) dollars.  Ortofon has been suggested and that is a good alternative.  I am suggesting AT instead because of your stated preference of high frequency extension.  Ortofons are more neutral, AT will be a bit brighter.  Both are excellent quality.

While my digital music collection numbers in the tens of thousands of tracks, my vinyl collection is quite modest (50 or so albums). As a result, I’ve never invested much in my TT setup.

You have to invest in analog and you need a better turntable, it’s pretty esy to solve the problem and purchase Technics SL1200GR (at least).

... if a cartridge can emphasize HF extension, that’s something I’d be interested in.

If you want a phono cartridge that can reproduce 10Hz - 50 000 Hz then you have to look ONLY for the cartridges with the most advanced stylus profile and high compliance! So the stylus must be something like MicroLine, MicroRidge, VdH, F.Gyger, Replicant-100, Line Contacct, Shibata, FineLine, Stereohedron ... just to give you some names. Cartridge compliance must be over 25cu @10Hz. Taking in count all these i believe you need an MM or MI cartridge with super lightweight cantilever like Titanium, Beryllium, Boron ... Those MM cartridges are not cheap! For more airy presentation you have to load them at 100k Ohm (instead of 47k Ohm which is ok too) and i’m pretty sure on Technics SL1200GR or SL1200G your analog rig will be better than digital.

Just like DACS, they all sound the same.

DAC’s don’t all sound the same, and I’m fully aware that analog sources and equipment in general are more sensitive to small changes. 

Appreciate the advice so far, including the recommendation of getting a “wheel of steel”, that’s in my eventual purchases list. 


In the meantime, I’ve bid on a Pro-Ject RPM 1 with Sumiko Pearl cartridge that’s listed here on AudioGon, which I believe would be a very meaningful upgrade from the vintage Marantz. 

As for the “why”, for me it’s more of a “why not?”. I enjoy music in general, my goals don’t include outperforming my digital front end, vinyl to me is a more tactile and involved medium that requires additional interaction with your system, which I enjoy.